import java.util.Stack;

public class Mystack {
    //为什么不能直接public Stack<Integer> stack1 = new Stack<>();跟stack2
    public Stack<Integer> stack1;
    public Stack<Integer> stack2;

    public Mystack() {
        stack1 = new Stack<>();
        stack2 = new Stack<>();
    }


    public void push(int x) {
        stack1.push(x);
    }

    public int pop() {
        if (empty()) {
            return -1;
        }
        if (stack2.empty()) {
            while (!stack1.empty()) {
                stack2.push(stack1.pop());
            }
            return stack2.pop();
        } else {
            return stack2.pop();
        }
    }

    public int peek() {
        if (empty()) {
            return -1;
        }
        if (stack2.empty()) {
            while (!stack1.empty()) {
                stack2.push(stack1.pop());
            }
            return stack2.peek();
        } else {
            return stack2.peek();
        }
    }

    public boolean empty() {
        return stack1.isEmpty() && stack2.isEmpty();
    }
}
